<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
    //   const str = 'hello,world'
      function test(str,keyword){
        //   return str.replace('/'+keyword+'/'+'gi', 'W')
          return str.replace(new RegExp(keyword)+'gi', 'W')
      }
    //   let res = str.replace(/w/gi, 'W')
      console.log(test('hello,world','w'))
    </script>
  </body>
</html>
